pjax = pushState + ajax

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Introduction

pjax is a jQuery plugin that uses ajax and pushState to deliver a fast browsing experience with real permalinks, page titles, and a working back button.

pjax works by grabbing html from your server via ajax and replacing the content of a container on your page with the ajax'd html. It then updates the browser's current URL using pushState without reloading your page's layout or any resources (JS, CSS), giving the appearance of a fast, full page load. But really it's just ajax and pushState.

For browsers that don't support pushState pjax fully degrades.

Overview

pjax is not fully automatic. You'll need to setup and designate a containing element on your page that will be replaced when you navigate your site.

Consider the following page.

<!DOCTYPE html>
<html>
<head>
  <!-- styles, scripts, etc -->
</head>
<body>
  <h1>My Site</h1>
  <div class="container" id="pjax-container">
    Go to <a href="/page/2">next page</a>.
  </div>
</body>
</html>

We want pjax to grab the URL /page/2 then replace #pjax-container with whatever it gets back. No styles or scripts will be reloaded and even the <h1> can stay the same - we just want to change the #pjax-container element.

We do this by telling pjax to listen on a tags and use #pjax-container as the target container:

$(document).pjax('a', '#pjax-container')

Now when someone in a pjax-compatible browser clicks "next page" the content of #pjax-container will be replaced with the body of /page/2.

Magic! Almost. You still need to configure your server to look for pjax requests and send back pjax-specific content.

The pjax ajax request sends an X-PJAX header so in this example (and in most cases) we want to return just the content of the page without any layout for any requests with that header.

Here's what it might look like in Rails:

def index
  if request.headers['X-PJAX']
    render :layout => false
  end
end

If you'd like a more automatic solution than pjax for Rails check out Turbolinks.

Also check out RailsCasts #294: Playing with PJAX.

Installation

bower

Via Bower:

$ bower install jquery-pjax

Or, add jquery-pjax to your app's bower.json.

  "dependencies": {
    "jquery-pjax": "latest"
  }

standalone

pjax can be downloaded directly into your app's public directory - just be sure you've loaded jQuery first.

curl -LO https://raw.github.com/defunkt/jquery-pjax/master/jquery.pjax.js

WARNING Do not hotlink the raw script url. GitHub is not a CDN.

Dependencies

Requires jQuery 1.8.x or higher.

Compatibility

pjax only works with browsers that support the history.pushState API. When the API isn't supported pjax goes into fallback mode: $.fn.pjax calls will be a no-op and $.pjax will hard load the given URL.

For debugging purposes, you can intentionally disable pjax even if the browser supports pushState. Just call $.pjax.disable(). To see if pjax is actually supports pushState, check $.support.pjax.

Usage

`$.fn.pjax`

Let's talk more about the most basic way to get started:

$(document).pjax('a', '#pjax-container')

This will enable pjax on all links and designate the container as #pjax-container.

If you are migrating an existing site you probably don't want to enable pjax everywhere just yet. Instead of using a global selector like a try annotating pjaxable links with data-pjax, then use 'a[data-pjax]' as your selector.

Or try this selector that matches any <a data-pjax href=> links inside a <div data-pjax> container.

$(document).pjax('[data-pjax] a, a[data-pjax]', '#pjax-container')

Arguments

The synopsis for the $.fn.pjax function is:

$(document).pjax(selector, [container], options)

selector is a string to be used for click event delegation.
container is a string selector that uniquely identifies the pjax container.
options is an object with keys described below.

pjax options

key	default	description
`timeout`	650	ajax timeout in milliseconds after which a full refresh is forced
`push`	true	use pushState to add a browser history entry upon navigation
`replace`	false	replace URL without adding browser history entry
`maxCacheLength`	20	maximum cache size for previous container contents
`version`		a string or function returning the current pjax version
`scrollTo`	0	vertical position to scroll to after navigation. To avoid changing scroll position, pass `false`.
`type`	`"GET"`	see $.ajax
`dataType`	`"html"`	see $.ajax
`container`		CSS selector for the element where content should be replaced
`url`	link.href	a string or function that returns the URL for the ajax request
`target`	link	eventually the `relatedTarget` value for pjax events
`fragment`		CSS selector for the fragment to extract from ajax response

You can change the defaults globally by writing to the $.pjax.defaults object:

$.pjax.defaults.timeout = 1200

`$.pjax.click`

This is a lower level function used by $.fn.pjax itself. It allows you to get a little more control over the pjax event handling.

This example uses the current click context to set an ancestor as the container:

if ($.support.pjax) {
  $(document).on('click', 'a[data-pjax]', function(event) {
    var container = $(this).closest('[data-pjax-container]')
    $.pjax.click(event, {container: container})
  })
}

NOTE Use the explicit $.support.pjax guard. We aren't using $.fn.pjax so we should avoid binding this event handler unless the browser is actually going to use pjax.

`$.pjax.submit`

Submits a form via pjax.

$(document).on('submit', 'form[data-pjax]', function(event) {
  $.pjax.submit(event, '#pjax-container')
})

`$.pjax.reload`

Initiates a request for the current URL to the server using pjax mechanism and replaces the container with the response. Does not add a browser history entry.

$.pjax.reload('#pjax-container', options)

`$.pjax`

Manual pjax invocation. Used mainly when you want to start a pjax request in a handler that didn't originate from a click. If you can get access to a click event, consider $.pjax.click(event) instead.

function applyFilters() {
  var url = urlForFilters()
  $.pjax({url: url, container: '#pjax-container'})
}

Events

All pjax events except pjax:click & pjax:clicked are fired from the pjax container, not the link that was clicked.

event	cancel	arguments	notes
event lifecycle upon following a pjaxed link
`pjax:click`	✔︎	`options`	fires from a link that got activated; cancel to prevent pjax
`pjax:beforeSend`	✔︎	`xhr, options`	can set XHR headers
`pjax:start`		`xhr, options`
`pjax:send`		`xhr, options`
`pjax:clicked`		`options`	fires after pjax has started from a link that got clicked
`pjax:beforeReplace`		`contents, options`	before replacing HTML with content loaded from the server
`pjax:success`		`data, status, xhr, options`	after replacing HTML content loaded from the server
`pjax:timeout`	✔︎	`xhr, options`	fires after `options.timeout`; will hard refresh unless canceled
`pjax:error`	✔︎	`xhr, textStatus, error, options`	on ajax error; will hard refresh unless canceled
`pjax:complete`		`xhr, textStatus, options`	always fires after ajax, regardless of result
`pjax:end`		`xhr, options`
event lifecycle on browser Back/Forward navigation
`pjax:popstate`			event `direction` property: "back"/"forward"
`pjax:start`		`null, options`	before replacing content
`pjax:beforeReplace`		`contents, options`	right before replacing HTML with content from cache
`pjax:end`		`null, options`	after replacing content

pjax:send & pjax:complete are a good pair of events to use if you are implementing a loading indicator. They'll only be triggered if an actual XHR request is made, not if the content is loaded from cache:

$(document).on('pjax:send', function() {
  $('#loading').show()
})
$(document).on('pjax:complete', function() {
  $('#loading').hide()
})

An example of canceling a pjax:timeout event would be to disable the fallback timeout behavior if a spinner is being shown:

$(document).on('pjax:timeout', function(event) {
  // Prevent default timeout redirection behavior
  event.preventDefault()
})

Server side

Server configuration will vary between languages and frameworks. The following example shows how you might configure Rails.

def index
  if request.headers['X-PJAX']
    render :layout => false
  end
end

An X-PJAX request header is set to differentiate a pjax request from normal XHR requests. In this case, if the request is pjax, we skip the layout html and just render the inner contents of the container.

Check if there is a pjax plugin for your favorite server framework.

Response types that force a reload

By default, pjax will force a full reload of the page if it receives one of the following responses from the server:

Page content that includes <html> when fragment selector wasn't explicitly configured. Pjax presumes that the server's response hasn't been properly configured for pjax. If fragment pjax option is given, pjax will simply extract the content to insert into the DOM based on that selector.
Page content that is blank. Pjax assumes that the server is unable to deliver proper pjax contents.
HTTP response code that is 4xx or 5xx, indicating some server error.

Affecting the browser URL

If the server needs to affect the URL which will appear in the browser URL after pjax navigation (like HTTP redirects work for normal requests), it can set the X-PJAX-URL header:

def index
  request.headers['X-PJAX-URL'] = "http://example.com/hello"
end

Layout Reloading

Layouts can be forced to do a hard reload when assets or html changes.

First set the initial layout version in your header with a custom meta tag.

<meta http-equiv="x-pjax-version" content="v123">

Then from the server side, set the X-PJAX-Version header to the same.

if request.headers['X-PJAX']
  response.headers['X-PJAX-Version'] = "v123"
end

Deploying a deploy, bumping the version constant to force clients to do a full reload the next request getting the new layout and assets.

ropean/jquery-pjax